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 The gene, identified in a recent Plant Biotechnology Journal
study, controls a critical piece of senescence, or seasonal
die-back, in corn. When the gene is turned off, field-grown
elite hybrids yielded 4.6 bushels more per acre on average than
standard plants.
Dating back to 1896, the Illinois experiment was designed to
test whether corn grain composition could be changed through
artificial selection, a relatively new concept introduced by
Charles Darwin just 37 years earlier. Repeated selection of
high- and low-protein corn lines had the intended effect within
about 10 generations. As selection for the traits continued,
however, additional changes were noticeable.
“One of the things that was noted as early as the 1930s was that
the low-protein line stays greener longer than the high-protein
line. It’s really obvious,” says Stephen Moose, professor in the
Department of Crop Sciences at Illinois and co-author of the
study.
Staying green longer into the season can mean more yield. The
plant continues photosynthesizing and putting energy toward
developing grain. But, until now, no one knew the specific gene
responsible for the stay-green trait in corn.
"The stay-green trait is like a ‘fountain of youth’ for plants
because it prolongs photosynthesis and improves yield,” says
Anne Sylvester, a program director at the National Science
Foundation, which funded this research. “This is a great basic
discovery with practical impact."
The discovery of the gene was made possible through a
decade-long public-private partnership between Illinois and
Corteva Agriscience. Moose and Illinois collaborators initially
gave Corteva scientists access to a population derived from the
long-term corn protein experiment with differences in the
stay-green trait. Corteva scientists mapped the stay-green trait
to a particular gene, NAC7, and developed corn plants with low
expression for the trait. Like the low-protein parent, these
plants stayed green longer. They tested these plants in
greenhouses and fields across the country over two field
seasons.
Not only did corn grow just fine without NAC7, yield increased
by almost 5 bushels per acre compared to conventional hybrids.
Notably, the field results came without added nitrogen
fertilizer beyond what farmers typically use.
“Collaborating with the University of Illinois gives us the
opportunity to apply leading-edge technology to one of the
longest running studies in plant genetics,” says Jun Zhang,
research scientist at Corteva Agriscience and co-author of the
study. “The insights we derive from this relationship can result
in more bushels without an increase in input costs, potentially
increasing both profitability and productivity for farmers.”
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Moose’s team then sequenced the NAC7 gene in the
high- and low-protein corn lines and were able to figure out just
how the gene facilitates senescence and why it stopped working in
the low-protein corn.
“We could see exactly what the mutation was. It seems to have
happened sometime in the last 100 years of this experiment, and
fortunately has been preserved so that we can benefit from it now,”
Moose says.
He can’t say for sure when the mutation occurred, because in the
1920s crop sciences faculty threw out the original seed from 1896.
“They had no way of knowing then that we could one day identify
genes controlling these unique traits. But we have looked in other
corn and we don’t find this mutation,” Moose says.
Future potential for this innovation could include commercialized
seed with no or reduced expression of NAC7, giving farmers the
option for more yield without additional fertilizer inputs.
Moose emphasizes the advancement couldn’t have happened without both
partners coming to the table.
“There’s value to the seed industry and society in doing these
long-term experiments. People ask me why university scientists
bother doing corn research when companies are doing it,” he says.
“Well, yeah they are, and they can do things on a larger and faster
scale, but they don’t often invest in studies where the payoffs may
take decades.”
The article, “Identification and characterization of a novel
stay-green QTL that increases yield in maize,” is published in Plant
Biotechnology Journal [DOI: 10.1111/pbi.13139]. Authors include Jun
Zhang, Kevin A. Fengler, John L. Van Hemert, Rajeev Gupta, Nick
Mongar, Jindong Sun, William B. Allen, Yang Wang, Benjamin Weers,
Hua Mo, Renee Lafitte, Zhenglin Hou, Angela Bryant, Farag Ibraheem,
Jennifer Arp, Kankshita Swaminathan, Stephen P. Moose, Bailin Li,
and Bo Shen. The research was funded by DuPont Pioneer, which is now
part of Corteva Agriscience™, and the Plant Genome Research Program
of the National Science Foundation. The Department of Crop Sciences
is part of the College of Agricultural, Consumer and Environmental
Sciences at Illinois.
[Source: Stephen Moose
News writer: Lauren Quinn]
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